As an agent for treating diabetes, various biguanide compounds and sulfonylurea compounds have been used. However, biguanide compounds are now hardly used because of their side effect of lactic acid acidosis. Although sulfonylurea compounds have potent hypoglycemic activity, they often cause serious hypoglycemia and must be used with care.
Thiazolidinedione derivatives having hypoglycemic activity and blood lipid lowering activity without the above disadvantages have been known. For example, JP-A 61-85372, JP-A 1-272573, JP-A 1-272574, JP-A 3-2173, JP-A 4-66579, JP-A 4-69383, JP-A 6-157522, etc., disclose 2,4-thiazolidinedione derivatives having at the 5-position a substituent such as a benzyl group or an arylmethyl group substituted by a substituted aromatic ring, etc.